In this study, we report the mechanical, structural, electronic, magnetic and optical behaviors in Zn1-xMnxS (0 <= x <= 1), which are determined by employing Wein2K code. The ferromagnetic (FM) state stability of the Zn1-xMnxS alloys has been elucidated from the calculated values of enthalpy of formation. The elastic constant (C-11, C-12, C-14) are calculated to find various useful mechanical parameters, which depend upon Mn concentrations. The calculated electronic band structure and density of states (DOS) have demonstrated that exchange splitting through p-d hybridization, arising due to Mn impurities, stabilize a ferromagnetic state. The exchange splitting of the bands is further elucidated from the sharing of magnetic moment, charge and spin, between the impurity cations and the host lattice anions. Various parameters like direct spin-exchange splitting Delta(x)(d), exchange constants N-0 alpha and N-0 beta have also confirmed a stable ferromagnetic state. Various calculated optical parameters have indicated that the studied compounds respond to visible and ultraviolet energies. Moreover, the calculated optical band gap and static dielectric constant epsilon(1) (0) verify Penn's model. The studied compounds of Zn1-xMnxS have been shown theoretically that they find potential spintronic and optical device applications. (C) 2016 Elsevier B.V. All rights reserved.